KR20180000008A - Method for controlling air-fuel ratio of vehicle - Google Patents

Abstract

A method of controlling an air-fuel ratio of a vehicle according to the present invention may include: comparing, by a control portion, a torque required by a driver with predetermined set torque; calculating, by the control portion, an advance amount of an ignition timing and a target air-fuel ratio in accordance with the required torque in response to the comparison result that the required torque is greater than the predetermined set torque; and advancing, by the control portion, the ignition timing by the advance amount after the calculating, and controlling the air-fuel ratio of the vehicle to be the target air-fuel ratio.

Description

METHOD FOR CONTROLLING AIR-FUEL RATIO OF VEHICLE [0002]

The present invention relates to a method of controlling an air-fuel ratio of a vehicle that improves engine performance by varying the air-fuel ratio of the vehicle in accordance with a required torque of the vehicle.

The EMS (Engine Management System) realizes the torque required for the engine through variable control of the throttle valve, ignition time and fuel amount control of the engine.

Generally, the fuel amount control is based on the stoichiometric air-fuel ratio ([lambda] = 1). However, when a high torque is required, which is hard to realize due to variable air volume, the air-fuel ratio is made rich .

For this, conventionally, when the torque required by the engine exceeds a certain standard, control is performed to uniformly control the air-fuel ratio to a predetermined value, which causes a significant reduction in the combustion efficiency of the engine and unnecessary fuel consumption occurs .

It should be understood that the foregoing description of the background art is merely for the purpose of promoting an understanding of the background of the present invention and is not to be construed as an admission that the prior art is known to those skilled in the art.

KR 10-1999-0059828 A

SUMMARY OF THE INVENTION The present invention has been proposed in order to solve such a problem, and it is an object of the present invention to provide a vehicle control system and a control method thereof, which can prevent an unnecessary fuel loss from being generated by variably controlling an ignition timing advance amount and an air- And a method of controlling the air-fuel ratio.

In order to accomplish the above object, the present invention provides a method for controlling an air-fuel ratio of a vehicle, wherein a control unit compares a required torque by a driver with a predetermined set torque: the comparison torque is greater than a preset torque The control unit calculating an advance amount of the ignition timing and a target air-fuel ratio according to the required torque; And after the calculating step, the control unit advances the ignition timing by the advance amount and controls the air-fuel ratio of the vehicle to the target air-fuel ratio.

Calculating a target torque which is a torque value obtained by subtracting a maximum torque that can be implemented when the air-fuel ratio is a stoichiometric air-fuel ratio at a required torque when the required torque is greater than a preset set torque; And a control unit for calculating an advance amount of the ignition timing and a target air-fuel ratio according to the target torque after calculating the torque.

The predetermined set torque may be set to a maximum torque that can be implemented when the air-fuel ratio is the stoichiometric air-fuel ratio.

And the control unit may control the vehicle at a stoichiometric air-fuel ratio when the required torque is equal to or less than a predetermined set torque as a result of the comparison.

According to the air-fuel ratio control method of the vehicle having the above-described structure, the air-fuel ratio and the ignition timing advance amount are linearly varied according to the torque required for the vehicle, thereby optimizing the combustion efficiency of the engine and improving the fuel efficiency of the vehicle.

1 is a block diagram showing an apparatus for controlling an air-fuel ratio of a vehicle according to an embodiment of the present invention;
2 is a flowchart showing a method of controlling the air-fuel ratio of a vehicle according to an embodiment of the present invention.

Hereinafter, a method for controlling an air-fuel ratio of a vehicle according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an apparatus for controlling an air-fuel ratio of a vehicle according to an embodiment of the present invention, and FIG. 2 is a flowchart showing a method for controlling an air-fuel ratio of a vehicle according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, a method of controlling an air-fuel ratio of a vehicle includes the steps of (S210): the controller 100 compares a predetermined torque with a predetermined torque by a driver; (S220) when the control unit 100 calculates the advance amount of the ignition timing and the target air-fuel ratio according to the required torque when the control unit 100 determines that the target air-fuel ratio is larger than the predetermined set torque. And a step S230 of causing the controller 100 to advance the ignition timing by the advance amount and to control the air-fuel ratio of the vehicle to the target air-fuel ratio after the calculating step S220.

When the torque required by the engine is continuously increased by the operation of the driver, the vehicle eventually enters the full load state. If the vehicle enters a full load state, the torque required for the engine suddenly rises and can be a torque value that can not be realized with the stoichiometric air-fuel ratio (lambda = 1).

Accordingly, the control unit 100 continuously compares the required torque by the driver with the predetermined set torque at step S210. When the vehicle is in a full load state, that is, when the required torque by the driver is the stoichiometric air- It can be judged whether or not it can not be implemented.

For example, the controller 100 may measure the required torque of the vehicle using a throttle position sensor (TPS). However, various techniques related to a method of calculating a required torque of a vehicle by a driver have been already known, and a method of calculating the required torque of the engine according to a designer may be implemented by varying the technique.

Generally, as a method of increasing the torque of the engine, a method of controlling the air-fuel ratio to be rich (? <1) or advancing the ignition timing is used. Accordingly, when it is confirmed through the comparison step S210 that the required torque is greater than the set torque, the control unit 100 of the present invention calculates the advance amount of the ignition timing and the target air-fuel ratio based on the measured required torque value (S220) By controlling the vehicle at the calculated advance amount and the target air-fuel ratio, the engine can be driven with the required torque (S230).

As described above, since the advance amount and the target air-fuel ratio are accurately calculated based on the measured required torque, the fuel combustion efficiency can be optimized and the fuel consumption can be improved accordingly.

More specifically, in the present technique, the calculating step S220 may be implemented when the controller 100 determines that the air-fuel ratio is the stoichiometric air-fuel ratio (λ = 1) when the required torque is greater than a predetermined set torque (S220-1) calculating a target torque which is a torque value obtained by subtracting the maximum possible torque from the target torque; and calculating the target torque, the control unit 100 calculates an advance amount of the ignition timing and a target air- (S220-2). &Lt; / RTI &gt;

This can be expressed as follows.

Here, the control unit 100 may measure the required torque through the comparison step S210, and the maximum torque value that can be implemented when the stoichiometric air-fuel ratio (lambda = 1) is mapped to the control unit 100 have.

The control unit 100 calculates a target torque, which is a torque value to be increased (S220-1), and calculates an ignition timing advance amount and a target air-fuel ratio for increasing the torque by the calculated target torque (S220-2) . At this time, the control unit 100 may directly calculate the advance amount and the target air-fuel ratio according to the target torque or may calculate the advance amount as a value mapped according to the target torque.

Therefore, the ignition timing advance amount or the air-fuel ratio is varied according to the required torque required by the driver and is controlled to be applied to the vehicle, so that the engine combustion efficiency can be improved and the vehicle running fuel economy can be improved.

The control unit 100 can advance the ignition timing by controlling the ignition device 130 based on the calculated advance amount and increase the fuel injection amount by the fuel injection device 140 to make the air-fuel ratio rich, &Lt; 1). At this time, the controller 100 can confirm whether or not the air-fuel ratio reaches the target air-fuel ratio through the oxygen sensor 120.

Meanwhile, the predetermined set torque may be set to a maximum torque that can be implemented when the air-fuel ratio is the stoichiometric air-fuel ratio ([lambda] = 1).

That is, the present technology is performed in a full load situation in which the maximum torque that can be implemented when the required torque by the driver is the theoretical air-fuel ratio (λ = 1) It is preferable that the maximum torque is set as a set torque value.

If it is determined that the required torque is equal to or less than the predetermined set torque as a result of the comparing step S210, the controller 100 may control the vehicle with the stoichiometric air-fuel ratio ([lambda] = 1).

That is, if the engine can implement the required torque of the driver without controlling the air-fuel ratio, the control unit 100 can secure the optimal combustion efficiency by controlling the air-fuel ratio to the stoichiometric air-fuel ratio (? = 1) (S240).

According to the air-fuel ratio control method of the vehicle having the above-described structure, the air-fuel ratio and the ignition timing advance amount are linearly varied according to the torque required for the vehicle, thereby optimizing the combustion efficiency of the engine and improving the fuel efficiency of the vehicle.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the following claims It will be apparent to those of ordinary skill in the art.

100:
110: Throttle position sensor
120: oxygen sensor
130: Ignition device
140: fuel injection device

Claims (4)

The control unit compares the required torque by the driver with the predetermined set torque:
Calculating, as a result of the comparison, an ignition timing advance amount and a target air-fuel ratio according to a required torque when the required torque is greater than a predetermined set torque; And
And controlling the air-fuel ratio of the vehicle to the target air-fuel ratio by advancing the ignition timing by the advance amount after the calculating step. The method according to claim 1,
Wherein,
Calculating a target torque that is a torque value obtained by subtracting a maximum torque that can be implemented when the air-fuel ratio is a stoichiometric air-fuel ratio at a required torque when the required torque is greater than a predetermined set torque;
And calculating a target air-fuel ratio based on the target torque, wherein the control unit calculates an advance amount of the ignition timing and a target air-fuel ratio according to the target torque. The method of claim 2,
Wherein the predetermined set torque is set to a maximum torque that can be implemented when the air-fuel ratio is the stoichiometric air-fuel ratio. The method according to claim 1,
Wherein the control unit controls the vehicle at a stoichiometric air-fuel ratio when the required torque is equal to or less than a predetermined set torque as a result of the comparison.

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